Abstract: A method of measuring a height of a fuel in an aircraft fuel tank (21)b including illuminating the fuel in the aircraft fuel tank and detecting reflected light from the fuel. Optical coherence tomography is used to determine the height of a surface of fuel in the fuel tank. An apparatus (30) is used to measure a height of a surface of fuel in an aircraft fuel tank, and an aircraft fuel tank system with a fuel tank and an apparatus for measuring a height of a surface of fuel in the aircraft fuel tank.

Abstract: Embodiments of the invention comprise apparatus and methods for detecting the presence of a substance in a test material using a plurality of wavelength-specific couplers (e.g. tilted fiber gratings) which provide a spatially distributed multi-node all-optical measurement system. Each node of the measurement system can comprise an optical module that is sensitive to the intensity of a limited band of wavelengths. The node is thus capable of detecting the presence of an absorption peak in a spectrum without having to obtain the full spectrum. By providing a plurality of optical modules that are sensitive to different wavelengths, the spectral signature of different substances may be monitored without having to measure full spectra. The measurement system may be particularly useful in a process control environment where it is desirable to take measurements of one or more substances in different locations.

Abstract: A method of measuring a height of a fuel in an aircraft fuel tank (21) b including illuminating the fuel in the aircraft fuel tank and detecting reflected light from the fuel. Optical coherence tomography is used to determine the height of a surface of fuel in the fuel tank. An apparatus (30) is used to measure a height of a surface of fuel in an aircraft fuel tank, and an aircraft fuel tank system with a fuel tank and an apparatus for measuring a height of a surface of fuel in the aircraft fuel tank.

Abstract: Embodiments of the invention comprise apparatus and methods for detecting the presence of a substance in a test material using a plurality of wavelength-specific couplers (e.g. tilted fibre gratings) which provide a spatially distributed multi-node all-optical measurement system. Each node of the measurement system can comprise an optical module that is sensitive to the intensity of a limited band of wavelengths. The node is thus capable of detecting the presence of an absorption peak in a spectrum without having to obtain the full spectrum. By providing a plurality of optical modules that are sensitive to different wavelengths, the spectral signature of different substances may be monitored without having to measure full spectra. The measurement system may be particularly useful in a process control environment where it is desirable to take measurements of one or more substances in different locations.

Abstract: A torsion sensor using an optical waveguide in optical communication with a diffraction grating, preferably a tilted grating, and most preferably a tilted Bragg grating, which provides the optical waveguide and grating with a torsion-dependent collective optical transmission spectrum. Changes in the collective optical transmission spectrum of the waveguide and grating, induced by changes in the amount of torsion applied to the waveguide, may be detected by detecting a corresponding change in the intensity of optical radiation transmitted through the grating from a controlled optical source. The degree of change in the collective optical transmission spectrum is dependent upon the degree of torsion (twist) applied to the optical waveguide. Measuring the magnitude and/or sense (i.e. increase/decrease) in the intensity of optical radiation transmitted through the grating from an optical source enables torsion to be sensed.